Mallards in Florida during the spring and summer originated from captive-reared stock. We consider these semi-domestic mallards, which are proliferating, a serious threat to Florida's wild waterfowl. Numerous diseases, including duck plague and fowl cholera, have been linked specifically to domestic or captive-raised waterfowl, and are easily transmissible to wild ducks. The potential for such an outbreak is a biological concern. Another significant threat of mallards is the genetic introgression of mallards into Florida's mottled duck population (see hybridization below).
Dealing with nuisance mallards is more complicated than controlling muscovies. If mallards are obvious hybrids with muscovies or other domestic ducks (see photo below), then no federal or state wildlife laws protect them from capture or direct population control. These hybrids may be moved to a captive situation where they would not come into contact with wild birds, or humanely euthanized as a last resort. If, on the other hand, the mallards have plumage similar to true, wild-strain mallards, and the birds are not marked as captive reared (generally, either marked with a clipped hind toe or a seamless metal leg band), then the birds are protected under federal migratory bird regulations. Destroying eggs or directly controlling populations requires appropriate mallard control permits.
Feral mallards are mating with mottled ducks, producing a hybrid offspring. State biologists are observing more and more mixed flocks and mixed pairs in the wild and these. These hybrid offspring are fertile, which further compounds the problem. Every mallard released in Florida can potentially contribute to the hybridization problem and the result is that fewer and fewer pure-bred Florida mottled ducks are left each year. The complete hybridization could result in the extinction of the Florida mottled duck.
Hybridization - The problem and what you can do to help
Mottled duck profile page
Mallard Control Permits